Powder tester



Aug. 31, 1948. A. AFRlcANo POWDER TESTER Filed Jan. 18, 1946 Alf-re d Afrr 1:1111 n Patented Aug. 31, 1948 Alfred Africano, Cumberland, Md., assignor to the v United States of America as represented by the Secretary of War Application January 18, 1946. Serial No. 641,904

(Cl. 73-35) Y claims. 1

'This invention relates to powder testers and more particularly to shear-disk powder testers for lobtainingl partially burned samples of relatively large'size pow-der grains.

The conventional shear-disk tester used for making such tests consists essentially of an elongated cylindrical chamber having a conventional copper-ball pressure gage secured by means of an adapter at one :end and a nozzle for the discharge of gases generated by the burning propellant at the other end. The nozzle is screwed into the end of the cylinder, thereby securing -a shear-disk in location, the thickness of which determines the limit to which chamber pressure can increase before shearing of the disk and release of the pressure occurs. When the pressure in the cylvinder chamber exceeds this limit, the disk fails, releasing the pressure and thereby extinguishing the flame of the burning powder. Ignition is accomplished by means of a heating coil packed in black powder lying against the powder grain, the lead wires passing through a special fitting' in the pressure gage adapter.

With this tester, the partially burned sample of powder usually is ejected by the exhausting gases, but can be recovered by having a canvas screen set up at a distance from the nozzle to prevent it from being lost or broken by impact.

It is, therefore, the purpose of this invention to provide certain improvements to the above described apparatus which will result in the unburned powder being retained intact within the tester after failure of the shear-disk.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. 1 is a vertical longitudinal section through the testing device.

Fig. 2 is a vertical transverse section through the discharge nozzle.

Fig. 3 is an isometric View of the end portion of the spacer tube.

As shown in Fig. 1 the tester consists of a hollow cylinder I having an axial recess or combustion chamber 3, counterbored at one endas at 5 to form a shoulder 6. A thread 'l is provided in the counterbore 5 for threadably securing therein an adapter I'2 for holding a conventional copper-ball pressure gage (not shown). An opening 9 through the other end of -cylinder I is threaded as at Ill for receiving a, conventional spark plug 3l for ignition purposes.

A radially disposed opening I8 is provided through the wall of cylinder I opposite the midsection of axial recess 3, a cylindrical extension collar I9, llet welded to cylinder I, serving to extend the opening I8 outwardly from cylinder I.

An annular shear-disk adapter 20 is threadably secured in opening I8 adjacent the bottom thereof. A' discharge nozzle 2I is provided for threadable assembly in opening I8, forming with shear-disk adapter 20 a discharge passage 23, opening radially outwardly from the middle oi recess 3. A shear-disk 22 of the required thickness, depending ony the pressure desired, is assembled between the shear-disk adapter 20 and the nozzle 2I and serves as a closure means to seal the passage 23 until such time as gas pressure developed in the tester rises to the required amount and causes shearing of the disk. Nozzle 2I has two sets of diametrically disposed wrench holes 24 by means of which a wrench bar (not shown) is used to tighen the nozzle and thereby lock the sheardisk 22 tightly in position, or to remove the nozzle in order to replace the disk.

A powder grain retainer or spacer tube I3 in the form of a rod or bar is provided having a generally cylindrical opening I4 extending longitudinally therethrough. This opening is of somewhat larger diameter than the powder grains to be tested and is provided to hold the powder grain to be tested in the combustion chamber 3 during the test. Tube I3 has its longitudinal edges I5 rounded to produce a loose sliding t of the tube I3 in recess 3 of cylinder I'. The ends of spacer tube I'3 are slotted across the flats as at IB to provide passage way for the gases being discharged thereby providing sectionally equivalent passages from each end of cylindrical opening I 4 for escape of burned powder gases to the centrally located discharge passage 23.

In operation, a. Isingle stick or grain of powder 30 is placed midway in opening I4 in spacer tube I3, opening i4 being of somewhat greater diameter than the grain of powder to be tested'. Spacer tube I3 is then placed in recess 3 with one edge in alignment with the axis of discharge passage 23 and the pressure gage adapter I'2 with a copper-ball gage (not shown) is screwed into position in the end, a gasket 25 serving to make a tight seal. A spark plug 3| is screwed tightly into opening 9 and has the space around its electrodes packed with a line grade of black powder as shown at 32.

A shear-disk 22 of the thickness required for the test is then secured against shear-disk adapter 20 by nozzle 2|.

The tester is now ready to re. A current of the necessary voltage is passed through the spark plug 3| igniting the black powder 32 therein which in turn ignites the grain of smokeless Ipowder. As soon as the pressure resulting from the combustion of the powder exceeds the shear strength of the shear disk, the disk blows out and the ycompressed gases around the Apowder grain inside 'of spacer tube i3 lc'low out through slots I6 'in each end thereof, flowing along the ats of spacer tube I3 and passing out through discharge passage 23.

This sudden release of the pressureMext-inguishes the burning powder, the spacer tube I3 causing the powder gases to bre fdrawigioff equally from both ends of the powder 'sample instead of from a single end as in previous types of powder testers. tially `burned sample of powder lto'heejected when the shear:disk is blown out is thus en-y tirely eliminated, and itis consequently retained intact for subsequent examination. The pressure vdeveloped 'may be measured bythe deformation Yof a copper-ball suitably supported in adapter l2.-

It is apparent from the above that the structure herein rshown and described provides a emeans vwhereby the unhurned portion of `t-he powder will be retained intact'within the tester after failure of the shear-disk.

I claim:

il.v In a propellent powder tester of `the type comprising an elongated hollow yhousing Yhaving at onev end an ignition means, at the other end a force'measuring means and a rupturable cloysureimedially of the longitudinal extent of the housing, the rimprovement comprising a hollow elongated specimen holder received in the hous- 4 ing, its exterior defining, with the interior of the housing free longitudinal passages for the transmission of gases from the ends of the holder to the rsaid closure.

2. A tester, as in claim 1, said holder having kerfs in the end faces.

3 4Inl a )propellent powderte'ster of the type comprising an elongated 'housing having a bore of vcircular section'and having'at one enden igniti'on means, at the other end a force measuring "means and a rupturable closure medially of the The tendency for the par 'aereas-screen@ The'follo'wing refcrencesare of record 4inthe iile' of this patent:

yUNITED' STTEs PATENTS 

